I have just been reading "Days of Rain" by Rebecca Stott, about her upbringing, and that of her father, in the Exclusive Brethren. This author covers all the same points and, yes, he has a book about his experience in, and leaving, the Brethren. For her, and I assume for him, in was tragically painful.
The thing that really got me angry about the Brethren is the sheer hypocrisy. For all the talk of morality and being right with God, they are not above having $millions stashed away in bank accounts for the benefit of their leaders, evade taxes everywhere, and carry on regardless of the psychological suffering they cause, even up to the point of suicide.
Look out for them influencing your politicians too. Here in the UK, they'll provide large numbers of volunteers to do the door-to-door canvassing for (normally Conservative)
candidates who'll advocate for their shady practices.
Edit: for clarity, I should say that the Open Brethren are a separate arm and are a far more bona fide Christian denomination.